Most international experts monitoring the conflict use a general figure of over 500,000 deaths, but acknowledge that changing conditions and restricted access make it impossible to know. Many believe it could be higher.
Based on that estimate, which takes into account both civilian and combatant deaths, around 2.33 percent of Syria’s prewar population of 22 million has been killed.
At the start of the conflict, many journalists and diplomats had relied on the numbers from the Office of the United Nations High Commissioner for Human Rights, which worked with partners on the ground to tally figures. But the United Nations stopped officially counting in 2014, as the war intensified and became more complex.
“It was always a very difficult figure,” a spokesman, Rupert Colville, said at the time. “It was always very close to the edge in terms of how much we could guarantee the source material was accurate.”
In early 2016, the United Nations special envoy for Syria, Staffan de Mistura, said he believed an estimated 400,000 people had been killed. But Mr. de Mistura described it as an unrefined estimate based on earlier figures combined with recent reports of violence.
Now, most official communications from the United Nations simply cite “hundreds of thousands killed.”
While the numbers vary, all of the groups agree on two things: that the Syrian government is responsible for the majority of the civilian deaths, and that calculating the toll is challenging.
“We often talk about these numbers, whether it’s 400,000 or 500,000, but it’s also about the trauma that is behind each of these numbers,” said Mr. Moumtzis of the United Nations. “It has become almost mechanical, the number.”
He added: “It’s really just a cold figure, but behind it are lives.”